From 40be88a92e65eb237a3b455255514f9a98274467 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 8 Feb 2024 19:50:41 -0500
Subject: visionOS: Update deployment-target flag for Xcode 15.1 beta

Use the same flags Xcode adds for `XROS_DEPLOYMENT_TARGET`.  They are
`-target arm64-apple-xros1.0` and `-target arm64-apple-xros1.0-simulator`,
where `1.0` is the deployment target version.

Fixes: #25188
---
 Modules/Platform/Apple-Clang.cmake |  6 +++---
 Source/cmLocalGenerator.cxx        | 39 +++++++++++++++++++++++++++++++++++---
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/Modules/Platform/Apple-Clang.cmake b/Modules/Platform/Apple-Clang.cmake
index 57b3910..61a6cd2 100644
--- a/Modules/Platform/Apple-Clang.cmake
+++ b/Modules/Platform/Apple-Clang.cmake
@@ -26,10 +26,10 @@ macro(__apple_compiler_clang lang)
     set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "-mtvos-version-min=")
   elseif(_CMAKE_OSX_SYSROOT_PATH MATCHES "/AppleTVSimulator")
     set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "-mtvos-simulator-version-min=")
-    elseif(_CMAKE_OSX_SYSROOT_PATH MATCHES "/XROS")
-    set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "-mtargetos=xros")
+  elseif(_CMAKE_OSX_SYSROOT_PATH MATCHES "/XROS")
+    set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "--target=<ARCH>-apple-xros<VERSION_MIN>")
   elseif(_CMAKE_OSX_SYSROOT_PATH MATCHES "/XRSimulator")
-    set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "-mtargetos=xros")
+    set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "--target=<ARCH>-apple-xros<VERSION_MIN>-simulator")
   elseif(_CMAKE_OSX_SYSROOT_PATH MATCHES "/WatchOS")
     set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "-mwatchos-version-min=")
   elseif(_CMAKE_OSX_SYSROOT_PATH MATCHES "/WatchSimulator")
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 04d2f50..86c55f5 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1983,10 +1983,43 @@ void cmLocalGenerator::AddArchitectureFlags(std::string& flags,
         "CMAKE_" + lang + "_OSX_DEPLOYMENT_TARGET_FLAG";
       cmValue deploymentTargetFlag =
         this->Makefile->GetDefinition(deploymentTargetFlagVar);
-      if (cmNonempty(deploymentTargetFlag)) {
+      if (cmNonempty(deploymentTargetFlag) &&
+          // CMAKE_<LANG>_COMPILER_TARGET overrides a --target= for
+          // CMAKE_OSX_DEPLOYMENT_TARGET, e.g., for visionOS.
+          (!cmHasLiteralPrefix(*deploymentTarget, "--target=") ||
+           this->Makefile
+             ->GetDefinition(cmStrCat("CMAKE_", lang, "_COMPILER_TARGET"))
+             .IsEmpty())) {
+        std::string flag = *deploymentTargetFlag;
+
+        // Add the deployment target architecture to the flag, if needed.
+        static const std::string kARCH = "<ARCH>";
+        std::string::size_type archPos = flag.find(kARCH);
+        if (archPos != std::string::npos) {
+          // This placeholder is meant for visionOS, so default to arm64
+          // unless only non-arm64 archs are given.
+          std::string const arch =
+            (archs.empty() || cm::contains(archs, "arm64")) ? "arm64"
+                                                            : archs[0];
+          // Replace the placeholder with its value.
+          flag = cmStrCat(flag.substr(0, archPos), arch,
+                          flag.substr(archPos + kARCH.size()));
+        }
+
+        // Add the deployment target version to the flag.
+        static const std::string kVERSION_MIN = "<VERSION_MIN>";
+        std::string::size_type verPos = flag.find(kVERSION_MIN);
+        if (verPos != std::string::npos) {
+          // Replace the placeholder with its value.
+          flag = cmStrCat(flag.substr(0, verPos), *deploymentTarget,
+                          flag.substr(verPos + kVERSION_MIN.size()));
+        } else {
+          // There is no placeholder, so append the value.
+          flag = cmStrCat(flag, *deploymentTarget);
+        }
+
         flags += " ";
-        flags += *deploymentTargetFlag;
-        flags += *deploymentTarget;
+        flags += flag;
       }
     }
   }
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